1. Field of the Invention
The present invention relates to a device for internal combustion engines which prevents evapotranspiration of fuel.
2. Description of Related Art
Generally, a fuel tank for a vehicle or other motorized equipment includes a fuel pump. Furthermore, as described in U.S. Pat. No. 4,672,937, some devices include a sub-tank within a fuel tank for maintaining a sufficient fuel level, even when the level of the fuel tank lowers. Furthermore, a fuel pump disposed in such a sub-tank prevents vapor-lock caused by a lowered fuel level.
The device disclosed in the Japanese Examined Utility Model Publication 3-46219 stores in its sub-tank the fuel of a low volatility returned from the internal combustion engine and sends it to the engine when the temperature is high, so as to prevent a vapor-lock from being caused by the vaporization of fuel in the fuel system.
However, the above-described devices have a problem in that, since excessive fuel of a high temperature (of low volatility) returned from the internal combustion engine is stored in a part of the fuel tank (that is, in a sub-tank), the temperature of that part of the stored fuel becomes higher. If the temperature of the stored fuel returned from the engine exceeds the boiling point of the liquid fuel, the generation of vaporized fuel rapidly increases.
Another problem is that if there is a difference in temperature between the liquid fuels in the main tank and the sub-tank, when the fuel having the lower temperature (in the main tank) drops into fuel having a higher temperature (in the sub-tank) while, for example, the vehicle is cornering, a rapid increase in the generation of vaporized fuel, or a fuel splash, occurs.
The increased generation of vaporized fuel or the fuel splash results in an overflow of a canister used for adsorbing the vaporized fuel, thus releasing vaporized fuel into the surrounding atmosphere. The present invention is intended to solve the problem of unwanted discharge of vaporized fuel by preventing evapotranspiration of fuel.